Intraocular pressure (IOP) is generally measured at individual points and usually only once, but rarely more often, during office hours and with various different instruments. This is probably inadequate for diagnosis, assessment of progression, and therapeutic decision making, since the IOP is not a static measurement, but rather one that is subject to greater or lesser fluctuations over shorter or longer periods. This has prompted the desire for more regular or even continuous measurements. This can be achieved with self-tonometers (not discussed in this article) or by using electronic aids with sensors in the eye (invasive; in the intraocular lens, in the ciliary sulcus, on the iris, in the posterior or anterior chamber, suprachoroidal or subconjunctival) or on the eye (non-invasive; sensor contact lens). Despite numerous advances and miniaturisations, there is as yet still no continuous measurement technique (either invasive or non-invasive) that can be used routinely, but development of such a device is at an advanced stage.
Georg Thieme Verlag KG Stuttgart · New York.